Internally resilient tie for railway track

ABSTRACT

The Internally Resilient Railroad Tie consists of two independent booted blocks placed in a tie case, one under each rail. An elastomeric bottom pad is placed under each block inside the boot. The stiffness of the elastomeric bottom pad is varied to compensate for the variations of the overall stiffniess of the track that often involves under-lying materials that are difficult to access for modification or replacement. The mass of the block, suspended between the elastomeric bottom pad and the elastomeric rail pad, provides a damper action that along with the enhanced elasticity of the assembly reduces dynamic impact forces and abates vibrations. The damper system reduces the duration and significance of dynamic peak forces and vibrations. However, variations of any or all of the damper system&#39;s components can be used to compensate for the variations of the overall dynamic response of the track where needed. A block retainer facilitates lifting whole tie assembly by rail during track installation and maintenance, as well as releasing the blocks during replacements of the bottom elastomeric pad. In service, the block retainer preferably does not restrain elastomers and allows for the rail float. This feature leads to further reduction of track maintenance.  
     In weak soils, or where the carrying participation of ballast and/or surface soils is undesirable or unfeasible, the internally resilient ties can be placed on piles, pile caps, longitudinal beams, firm foundations, bridge decks and tunnel inverts because the internally resilient tie is capable of substituting for ballast action and for the elastic contributions of subgrade. Internally resilient ties are suitable for transition zones between ballasted and ballastless track zones.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] Not Applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not Applicable

REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTINGCOMPACT DISC APPENDIX

[0003] Not Applicable

BACKGROUND OF THE INVENTION

[0004] The elastic response of railway track, also referred to as trackstiffness, track elasticity or spring rate of the track, is oftenerratic. Also erratic is the dynamic response of the track due tovariations of the types and depths of subsurface materials. Suchirregularities lead to differences in the track's deflection under apassing train, and to variations in the dynamic response of the track.These differences dynamically excite rolling stock. The resulting forcesand vibrations lower comfort and safety of the travel, increase trackmaintenance intensity, constitute a major obstacle in the upgrading ofexisting track for higher speeds, and/or lead to speed restrictions.

[0005] Track stiffness variations caused by inaccuracies of upper trackstructure, which consists of rails, ties, ballast, and subballast, canbe controlled by routine track maintenance. However, the track stiffnessirregularities due to stiffness variations of subgrade and under-layingmaterials in situ are very difficult to address. Extensive excavationand replacement of soils located below the track are often necessary toobtain a track formation of desired uniformity and quality. Such workcannot be performed within track maintenance windows of an operatedrailroad line. Temporary closures of the line are necessary what is verydifficult to afford especially on heavily traveled lines.

[0006] Various attempts to influence track stiffness by the rail pad, anelastomer placed between the rail and the railway tie, or between therail and a tie plate, or a combination of the both, have been madewithout much success. The elastomeric rail pad must be very hard tosurvive at this location and to provide lateral stability of the rail. Arail pad sufficiently softened to provide the desirable and generallyreduced overall track resiliency cannot be used so that influencing theoverall stiffness of the track structure to achieve its overalluniformity at the rail pad's level is not practical. Various fastenershave been invented that introduce a second elastomer under a steel plateplaced on the top of the tie in addition to the rail pad. Thesefasteners do not include any stiffness adjustment features to compensatefor the random variations of the track stiffness due to the under-layingmaterials in situ. Also, the mass of the added plate is too small togenerate a damper phenomenon in its combination with the top and bottomelastomeric pads. The resulting lack of dampening within the trackstructure leads to intense dynamic loading effects, early deteriorationof such rail fastening features, and spread of objectionable vibrationsinto the environment.

[0007] Large occurrence of random variations of stiffness and variationsof the dynamic response of the track observed on majority of existingrailway lines prompted the providers of high-speed rail services inEurope and Japan to construct new lines. Strict standards were adoptedto ensure uniformity of subgrade and subsoil layers into considerabledepths, and to avoid poor soil areas. The presence of tight curves onexisting lines played smaller role in the decision-making process thangenerally perceived because many tight curves can be traveled fast usingtilting technology incorporated in certain high-speed trains. The randomvariations of overall track stiffness and its dynamic response lead torunning instabilities and increase track maintenance costs. Thesevariations constitute general impediments of the track quality andessential obstacles to high-speed operations. The previous art offersonly costly replacements of variable under-laying materials or theirmodifications in situ as remedies.

BRIEF SUMMARY OF THE INVENTION

[0008] This invention consists of an internally resilient tie (IRT) forrailway track and its alternatives. The internally resilient tie is adevice for achieving uniformity of elastic and dynamic response of thetrack system. It compensates for random stiffness variations of thetrack and its formation, enhances dampening, reduces dynamic impact andabates vibrations at an expanded frequency range so that vibrationsentering the surrounding environment are minimized.

[0009] The internal resiliency built into the concrete or steel railwaytie allows to adjust track stiffness to a desirable value, and tointentionally vary the spring rate and dynamic response of the tieassembly, at an added elastomeric level. The physical feature thatprovides the variability of internal resiliency, favorable dynamicresponse and dampening of the tie assembly is a booted block placedunder each rail and encased or inserted in a concrete or steel tie. Thisblock is supported by bottom elastomeric pad placed inside theelastomeric boot. The bottom elastomeric pad can be as soft asdetermined by the design, and its properties varied as needed while theelastomeric top pad under the rail can be as hard as necessary to endurehigh frequency dynamic effects and abrasion in its contact with therail. The block suspended between the two elastic members acts as adamper. The parameters of this dampening system are controlled by theproperties of the bottom elastomeric pad and by the block's mass.Variations of the properties of the bottom elastomeric pad are made insuch a manner that they compensate for site-specific random variationsof the overall stiffness of the track and its formation, and assist inthe compensation for the dynamic variations of the track's under-layingsoils and soil/rock interfaces. Also, the system is suitable fortransitions between track placed on soils and track on firm foundationssuch as bridge abutments, tunnel inverts and slabtrack.

[0010] Since the block is large, the size of the bottom elastomeric padis large as well. As a result, the unit stresses at the bottomelastomeric pad are small so that its fatigue life is very long.

[0011] The use of internally resilient ties will reduce or eliminate theneed to perform capital intensive excavations, as well as re-processing,partial or total replacement of soils to achieve uniformity of theirelastic and dynamic behavior when loaded by trains, and to dampen forcesat resonant frequencies.

[0012] The internally resilient ties are supported by ballast, or placedon piles, pile caps or other firm structural foundations what isparticularly advantageous in poor soil areas. This solution has apotential to reduce or eliminate conventional replacement of weak soils,their drainage, or construction of elevated structures. Internallyresilient ties are fully capable of substituting for ballast action.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0013] Drawing No. 1—Internally Resilient Tie with Independent BootedBlocks and Concrete Case. This drawing shows the alternative of bootedsteel, hybrid steel/concrete, wood or plastic blocks (2) encased in aconcrete tie case (1). This alternative is shown in a plan view (bottomof the drawing), in longitudinal section—Section A-A′—(top of thedrawing) and in a cross section—Section B-B′ (left middle area of thedrawing). The plan view and the sections are symmetrical about theircenterlines. The blocks (2) are independent of each other and placed inelastomeric enclosures-boots (4). The hard top elastomeric rail plate(5) is placed directly under the rail (3). The soft bottom elastomericplate (6) is placed inside the boot (4) under the block (2). The rail(3) is attached to the block, preferably with threadless elasticfasteners with spring clips (7). Threadless elastic spring clips (7)would likely lead to a lower track maintenance intensity thenalternative fasteners equipped with bolts and nuts. The fastening of therail to the block and its clips (7) are optional and do not constituteparts of this patent.

[0014] The block is prevented from being pulled up from the tie tofacilitate lifting the tie assembly by the rail during trackinstallation and maintenance. This feature is ensured by the function oftwo block retainers per block (8). A block retainer is a device thattransfers the vertical uplift force from the blocks to the tie case whenthe entire assembly is lifted by the rail. However, the block retaineris also capable of a complete withdrawal of the block (2) from the tiecase anytime the bottom elastomer (6) must be replaced, usually tocompensate for altered properties of under-laying materials.Furthermore, the block retainer (8) does not compress the elastomers (4,5,6), and does not restrain the block's (2) upward movement that isneeded to follow the rail's (2) uplift wave that exists at a certaindistance away from the location of its loading by a wheel. Otherwiseraising of the entire tie assembly would accelerate deterioration oftrack geometry that is common on a track equipped with conventionalties. Also, the block retainer (8) ensures that the length of the upwardtravel of each lifted block within the retainer's upward movementallowance is constant for all blocks.

[0015] Drawing No. 2 Internally Resilient Tie with Independent BootedBlocks and Steel Case. This drawing shows the alternative of bootedsteel, hybrid steel/concrete, wood or plastic blocks (2) encased orinserted in a steel tie case (1). This alternative is shown in a planview (bottom of the drawing), in longitudinal section—Section A-A′—(topof the drawing) and in a cross section—Section B-B′ (left middle area ofthe drawing). The plan view and the sections are symmetrical about theircenterlines.

[0016] Except for the tie case made of steel and the block retainerattached to it by a suitable means of steel to steel connection, allfeatures and their descriptions pertinent to this alternative are thesame as the ones described for the Alternative Internally Resilient Tiewith Independent Booted Blocks and Concrete Case, Drawing No.1.

[0017] Drawing No. 3 Detail of Section A-A′ Showing Retainer of claim18—Internally Resilient Tie with Independent Booted Blocks and ConcreteCase. This Drawing provides more clear view of the longitudinal sectionthrough the tie at one block and block retainer (8) than Drawing 1. Theblock retainer (8) consists of a cast-in shoulder with two spring steelleaf plates stated in the claim 18. However, other types of the blockretainer's design are possible to serve the same purpose and they arecovered under the Broad claim 16. This drawing also shows the featuresof the rain water diversion and enhancement of electrical insulationproperties of the block by the non-metallic collar (12) and by the shapeof the rubber boot's edge (4) of the Dependent claim 20.

[0018] Drawing No. 4 Detail of Section A-A′—Showing Block Retainer ofclaim 19—Internally Resilient Tie with Independent Booted Blocks andSteel Case. This Drawing provides more clear view of the longitudinalsection through the tie at one block and block retainer (8) than theDrawing 2. It consists of a bolted-on shoulder with two spring steelleave plates stated in the claim 19. However, other types of the blockretainer's design are possible to serve the same purpose and they arecovered under the Broad claim 16. This drawing also shows the featuresof the rain water diversion and enhancement of electrical insulationproperties of the block by the non-metallic collar (12) and by the shapeof the rubber boot's edge (4) of the Dependent claim 20.

[0019] Drawing No. 5 Plan view relevant to block retainers of claim 18and claim 19 —Internally Resilient Tie with Independent Booted Blocksand Concrete or Steel Case. This Drawing provides more enlarged planview of the booted block (2) cast into or inserted in a concrete orsteel case (1) and of the block retainers (8) of claims 18 and 19 whoseplan views in this projections are the same. However, other types of theblock retainer's design are possible to serve the same purpose and theyare covered under the Broad claim 16. This drawing also shows thenon-metallic collar (12) for the rain water diversion and enhancement ofelectrical insulation properties of the Dependent claim 20.

DETAILED DESCRIPTION OF THE INVENTION

[0020] The Internally Resilient Tie consists of the following componentsas shown on Drawings 1 through 5 to provide the purposes described asfollows:

[0021] A. Two Booted Booted Steel, Hybrid Steel/Concrete, Wood orPlastic Blocks (2) Placed in a Steel or Concrete Tie Case (1) Supportingthe Rail (3).

[0022] B. Rubber Boot (4), Top Elastomeric Rail Pads (5) and ElastomericBottom Pads (6).

[0023] This Internally Resilient Tie provides three-dimensionalresiliency at each rail. The vertical resiliency is separated into twolayers. The upper layer, a stiff rail pad (5) of standard hardness, isplaced between the rail (3) and the top of an independent booted block(2). This pad abates predominantly high frequency vibrations. The lowerlayer consists of an elastomeric pad (6) placed under the block withinthe boot (4). This pad abates predominantly low frequency vibrations.Lateral resiliency is provided by elastic response of the vertical sideof the boot (4). The booted blocks (2) have to be independent one of theother in order to allow development of the lateral resiliency of a blockin case that the rail (3) is impacted transversely by an unloaded wheel.If the booted blocks under the parallel rails were made of one piece orconnected together, the impacted block would not be able to dissipatekinetic energy by its lateral yielding. This is because the othervertically loaded wheel of the same axle would prevent the very smallbut indispensable side-way movement needed for the lateral dynamicimpact reduction purposes from occurring. As a result, the lateraldynamic forces critical for longevity of track fasteners would be muchhigher than in the case of independent booted blocks.

[0024] The internally resilient tie is an effective damper. Thedampening function is provided by the mass of the block (2) suspendedbetween the two elastomeric pads (5) and (6). Since many kinds ofresonance that exist in the railway track and become very pronounced athigh speeds cannot be fully eliminated, the effective dampening willreduce their duration and significance. In a broad sense, this inventionprovides means of operational speed range extension, and/or reductionsof track maintenance. In a narrow sense, the internally resilient tiesfor railway track improvement rail deflection uniformity by controllingthe total elastic response of the track by varying elasticity of thebottom elastomer within the resilient railway tie, in lieu of modifyingor replacing subgrade and/or subsoils under the track. Also, thisinvention facilitates the desirable increase of the track's nominalelasticity by selection of appropriate resiliency at the bottomelastomer within the tie, instead of an alternative introduction of asoft top rail pad. Applications of soft rail pads have been triedwithout much success in the past.

[0025] Internally resilient ties can be placed on ballast in atraditional manner, or used in ballastless applications. In weak soils,or where the carrying participation of ballast and/or surface soils isundesirable or unfeasible, the internally resilient ties can be placedon piles, pile caps, longitudinal beams, firm foundations, bridge decksor tunnel inverts because the internally resilient tie is fully capableof substituting for ballast action. Also, the internally resilient tiesprovide stiffness and dynamic response transition between ballasted andballastless kinds of railway track.

[0026] C. Elastic Rail Fastening Clips and Shoulders (7)

[0027] Any type of elastic rail fastenings (7) of a desired toe load canbe utilized to attach the rail (3) to the blocks (2). However, theserail fastenings should be preferably threadless to eliminate maintenancedifficulties associated with frozen bolts during track maintenance,namely rail replacement. Rail fastenings do not constitute a part ofthis patent.

[0028] D. Block Retainer

[0029] The block retainer (8) is attached to the concrete tie case (1)by its component placed inside the concrete of the tie case (1) as shownin the Drawing 3 for claim 18, or by a suitable steel to steelconnection in the case of steel tie case. Such a connection is thebolted-on shoulder shown in the Drawing 4 for claim 19. Except for thisbolt-on feature, otherwise thread-less block retainers would likely leadto lower track maintenance intensity than the ones relying on bolts andnuts.

[0030] a. Purposes Served by the Block Retainer

[0031]1. Vertical stop

[0032] In order to facilitate lifting of the tie assembly by attachedrails, that is necessary during its initial installation, tamping andreplacement by mechanized track maintenance equipment, a stop has to beused that prevents the blocks from being pulled up from the case. Also,the block retainer (8) ensures that the length of the upward travel ofeach lifted block within the retainer's upward movement allowance isconstant for all blocks. This would allow adjust standard tampingmachines for just one value of the travel to achieve proper trackgeometry during the track installation and maintenance. Otherwise everytie assembly would have to be tamped individually.

[0033]2. Rail float

[0034] A loaded rail deflects downward in the area of the applied wheelload and rises slightly at a certain distance from this point. Thisshape of the rail's deflection curve is characteristic of a beam onelastic supports. It is advantageous to allow the block to rise duringthe rail's uplift phase without allowing the tie case to rise becauseavoidance of any uplift at the tie/ballast interface leads to majorreduction of track maintenance. For this reason, the stop must notrestrict the block from its vertical movement completely. A sufficientspace must exist between the bottom surface of the restricting member ofthe vertical stop and the mating surface of the block. This rail floatfeature is the subject of claim 17.

[0035] b. Block Retainers Pertinent to Dependent claims 18 and 19, Parts(16) and (9) through (15). For ease of installation, and for avoidanceof difficult maintenance efforts associated with threaded componentsfrozen by corrosion, threadless devices such as driven flat springs(9,10) inserted into a curved slot in a cast iron insert (16) are used,as shown on the attached drawings. During installation, the lower springleaf (9) is inserted first. Then the upper leaf (10) is driven in. Itdeflects and causes the leaf (9) to deflect as well. The leaves (9) and(10) stay within the slot by thus introduced pre-load. An eventualshifting of the leaves that would loosen the plates is prevented by thepin (11) inserted into the aligned holes in the leaves (9) and (10) andthe shoulder (16). The contact point on the block's top can be loweredor raised by inserting member (14) of an adjusted depth into the slotcreated by two members (15).

[0036] E. Rain Water Diversion and Enhancement of Electrical InsulationProperties of the Block by the Non-Metallic Collar (12) and by the Shapeof the Rubber Boot's Edge of the Dependent Claim 20

[0037] The insulating non/metallic collar (12) is provided around theentire perimeter of the block to keep rainwater from entering the tie'sinterior along the vertical surfaces of the boot.

[0038] The dry surfaces under the overhang of the insulatingnon/metallic collar (12) and under the lip of the rubber boot (4) willenhance the electrical insulating properties of rail fasteners, and theprotection against the surface leakage of stray currents on electrifiedlines.

[0039] F. Procedure for IRT Application in the Areas of Relatively GoodSub-Soils to Achieve Uniformity of Vertical Stiffness of the Track thatis Necessary for High-Speed Rail Operations:

[0040] In order to ensure successful incremental upgrading of existingrailway lines for high speed operations, upgrading of the uniformity ofthe elastic and dynamic response of the track is necessary. It shall beachieved as follows:

[0041] a. The existing vertical track stiffness shall be determined ateach tie

[0042] b. The desired uniformity of the track shall be determined andcompared to the lowest stiffness measured. If this stiffness is stillacceptable for the relevant type of rail operations, then this stiffnessshall be accepted to become the nominal vertical stiffness of the track.

[0043] c. The tolerable deviation of the individual track stiffness fromits nominal value will be established

[0044] d. The necessary change of vertical stiffness will be calculatedat each tie to achieve the uniform nominal stiffness within thespecified tolerance.

[0045] e. Replacement pads corresponding to the individual values ofvertical stiffness will be determined and color-coded.

[0046] f. Ties will be marked with corresponding colors

[0047] g. The bottom pads (6) of each resilient concrete tie will bereplaced with pads of required hardness

1. What I claim as my invention is an internally resilient railroad tie,a tie containing two blocks placed in the tie case, independent of eachother, one under each rail, further equipped as follows: Each block isplaced in an elastomeric enclosure termed the boot. An elastomericbottom pad is placed under each block inside each boot. The elastomericbottom pad is supplied and applied in various values of stiffness tocompensate for the lack or excess of the overall track stiffness at eachtie location along the track. The mass of the block, the elastomericbottom pad, and an elastomeric rail pad placed on the top of the blockunder the rail create a damper, a system consisting of a mass suspendedbetween two elastic members. The properties of this damper system areadjustable by varying any or all of its components to compensate forvariations of the overall dynamic response of the track.
 2. The closureof claim 1 wherein the block is made of concrete
 3. The closure of claim1 wherein the block is made of steel
 4. The closure of claim 1 whereinthe block is made of cast iron
 5. The closure of claim 1 wherein theblock is made of a concrete/steel combination
 6. The closure of claim 1wherein the block is made of plastic
 7. The closure of claim 1 whereinthe block is made of wood
 8. The closure of claim 1 wherein the tie caseis made of concrete
 9. The closure of claim 1 wherein the tie case ismade of steel
 10. The closure of claim 1 wherein the tie case is made ofcast iron
 11. The closure of claim 1 wherein the tie case is placed onballast
 12. The closure of claim 1 wherein the tie case is placed onpiles
 13. The closure of claim 1 wherein the tie case is placed on pilecaps
 14. The closure of claim 1 wherein the tie case is placed onlongitudinal beams
 15. The closure of claim 1 wherein the tie case isplaced on a firm foundation such as rock, structural foundation createdfor this purpose, a tunnel invert or a bridge slab.
 16. What I claim asmy invention is the block of the internally resilient tie equipped witha block retainer, a device for retaining blocks in the tie when completerail tie assemblies are lifted and moved by the rail during trackinstallation and maintenance, and for releasing the blocks from the tiewhen the bottom elastomeric pad or the boot has to be replaced orremoved.
 17. The closure of claim 16 wherein the block retainer and theblock are not contiguous in service because the block retainer allowseach block to follow the deflection of elastomers and the uplift wave ofthe rail within certain travel.
 18. The closure of claim 16 wherein theblock retainer consists of cast iron insert equipped with a shank foranchorage in the concrete mass of the tie case, and with a curved slotat its top to receive spring leaves, held in the slot by their flexuralpre-loads and secured by a vertical pin inserted into aligned holes inthe leaves and in the shoulder as shown on the Drawing
 3. 19. Theclosure of claim 16 wherein the block retainer consists of cast ironinsert equipped with a threaded extension for its attachment to thesteel tie case, and with a curved slot at its top to receive springleaves, held in the slot by their flexural pre-loads and secured by apin inserted into aligned holes in the leaves and the shoulder as shownon the Drawing
 4. 20. What I claim as my invention is the block of theinternally resilient tie equipped with a device for rain water diversionand enhancement of electrical insulation properties of the block by thenon-metallic collar attached to the block's perimeter and/or by theoverhang-shaped elastomeric boot's edge to create dry areas under thecollar, and/or under the lip of the boot in order to interrupt surfacepassage of electric currents, and to keep rainwater from entering thetie's interior along the vertical surfaces of the boot.